Over the last decade, stem cells have gained tremendous attention for applications in regenerative medicine. The inherent ability of stem cells to self-renew and to differentiate into specialized cell types makes them an attractive area of research. Pluripotent stem cells (such as embryonic stem cells and induced pluripotent stem cells) have become especially popular since they can provide cells for essentially every tissue and organ in the body, making them a type of universal cell source. In particular, these cells hold great potential in neuroscience for the treatment of numerous nervous system disorders (e.g. Alzheimer's disease, Parkinson's disease, spinal cord injury) since they provide an unlimited source of engraftable neural cells. While pluripotent stem cells afford great opportunities for exploring the devastating deficiencies in neuro-regenerative medicine, controlling stem cell fate towards specific neuronal cell lineage is one of the most pressing concerns to address before their therapeutic application can be fully realized.
To this end, the cellular microenvironment (composed of soluble signals, insoluble/physical signals and cell-cell interactions) plays a decisive role in regulating stem cell differentiation. However, the function of stem cell microenvironmental factors on differentiation is extremely difficult to investigate since these studies require extensive knowledge of multiple regulatory signals and how they interact to influence cellular function. While generous progress has been made in an attempt to address these concerns, the conventional methods currently available for such an investigation are still limited. At the same time, current therapy has seen the survival of only a small fraction of the stem cells or their differentiated cell types when implanted in vivo, due to inflammation and hypoxia present at the damaged site. In turn, several obstacles such as preparing engraftable homogenous neural cells and improving the ability to precisely control neural cell fate must be surmounted before innovative clinical approaches for neuro-regenerative medicine can be developed.